Multifunction, multiple target radar systems are required to perform search and target track functions, and may also be required to engage in electronic countermeasures, and may perform other functions. The number of targets may be very large in a worst-case scenario. Large amounts of electromagnetic energy are required to search for and track these multiple targets, some of which may be at considerable distances, and large amounts of signal processing capability are required to perform radar functions, and to sense and track the large numbers of targets.
It is important to control the scheduling of electromagnetic transmissions so that the operating power does not exceed that of which the radar is capable. Put another way, suboptimal energy or power resource control may reduce the ability to properly search for and track the targets. Similarly, the processing must be sufficient to perform all the radar-related tasks such as pulse duration control, target return pulse correlation, and also to perform scan-to-scan correlation and target tracking.
FIG. 1 is a simplified block diagram of a prior-art multifunction radar system 10. In FIG. 1, a radar antenna illustrated as 12 is coupled to a transmit/receive (T/R) arrangement illustrated as a block 14. A transmitter illustrated as a block 16 provides pulses to the antenna 12 by way of T/R 14 under control of a radar control computer (RCC) or processor 20. A well known Kalman filter 20k is illustrated as being associated with radar control processor 20. Electromagnetic signals are transmitted toward, and returned from, a representative target 22, one of potentially many such targets. The electromagnetic transmissions and returns are illustrated as a conventional lightning bolt symbol 13. The return signals are routed by T/R 14 to a radar receiver (RX) illustrated as a block 18. Block 18 performs well-known functions, including analog signal processing and conversion of the signals to digital form.
The processed and digitized radar return signals from radar receiver 18 are applied to a radar control computer (RCC) 20, which performs the tasks of scheduling transmissions from radar transmitter 16, and commanding the scheduled transmissions by means of commands applied over a path 24. The radar control computer also processes the received signals to minimize the signal-to-noise ratio and enhance detection, it may perform jamming countermeasures, and has many other very important tasks in signal processing. Once targets are identified, the radar control computer also attempts to make sense of the moment-to-moment target environment, including such tasks as controlling the radar searching of a volume for previously unknown targets, identifying targets in the presence of noise, correlating new positions of targets with previous positions to thereby define target tracks, and the like.
Among the tasks of the radar control computer 20 of FIG. 1 are those of directing an antenna beam (or beams in the case of multibeam antennas) toward each target during target tracking. It is important, when a target location is to be updated, that an antenna beam be directed toward the target's approximate position so that electromagnetic energy can be directed toward it, and so the reflections of energy from the target can be received for processing. If the target does not lie within an antenna beam, its new position will not be sensed, and tracking may fail. The beam direction for the next scheduled transmission is also sent from the radar control computer 20 of FIG. 1 to the transmitter 16 (and its associated antenna 12) to select the beam direction for each radar transmission.
FIG. 2 is a simplified diagram illustrating possible target locations within a radar beam. In FIG. 2, a radar system (not illustrated) is mounted on a ship 210 at an origin 211, at the intersection of beam-width-limit lines 212a and 212c. Beamwidth limit lines 212a and 212c are centered about a beam center line 212b. Different positions along lines 212a, 212b, and 212c represent different ranges from the origin 211, which is the location of the radar. Two different ranges are illustrated by dash line, namely ranges 214a and 214b. The included angle BW subtended between range lines 212a and 212c represents the beamwidth of the radar beam at some reference response or power level from the peak response or power level, such as the half-power level (−3 dB) as known in the art. At the range represented by dash line 214a of FIG. 2, the target is represented as being at a position indicated as 218. The location 218 lies within the angle BW, so that the target will receive incident electromagnetic energy and reflect the energy in an amount that will result in detection of the target after the signal processing performed in the radar control computer 20 of FIG. 1. At the range represented by dash line 214b of FIG. 2, the location of the target is illustrated as 220. Location 220 is without the angle BW subtended between the beamwidth limit lines 212a and 212c. 
Improved or alternative radar arrangements are desired.